Switching device



June 15, 1965 w. 'r. ACKERMANN SWITCHING DEVICE Filed Dec. 31, 1962 VENTOR. M41124 Ig y/2474mm Imam-" United States Patent 3,189,709 SWITCHTNG DEVICE Walter T. Ackermann, Millington, NJ, assignor to Radio Corporation of America, a corporation of Delaware Filed Dec. 31, 1962, Ser. No. 248,391 11 Claims. (Cl. zed-r12 This invention relates generally to switching devices, and more particularly to an electrically operated switch of the type wherein a small quantity :of mercury is adapted to make and break an electrical connection between electrical conductors. The switching device of the present invention is particularly useful for interrupting a unidirectional current in a manner whereby the interrupted current can be transformed by a transformer, as, for example, in an inverter circuit.

Electrically operated switches, such as vibrators of the buzzer type, for example, have been proposed for interrupting an electric current periodically. While these vibrators are suitable for many applications, each one operates at a relatively fixed frequency that is determined, in part, by the mechanical resonance of its vibrating reed. Prior art vibrators employ contact points that have a tendency to burn, thus rendering such vibrators inoperative in time. This is especially true when large currents are controlled by the vibrators. Also, the resultant waveform of the current interrupted by these vibrators is not variable, being substantially the same for each cycle of operation.

It is an object of the present invention to provide an improved switching device that is relatively free from the aforementioned disadvantages and limitations of prior art vibrators.

Another object of the present invention is to provide an improved switching device that is adapted to switch relatively high currents and to dissipate heat easily.

Still another object of the present invention is to provide an improved switching device whose frequency of switching may be controlled over a relatively wide range.

A further object of the present invention is to provide an improved switching device of the type described that is relatively simple in construction and operation, easy to manufacture, and highly efiicient in use.

Briefly, the improved switching device of the present invention comprises a pair of spaced-apart electrical conductors and insulating means on opposite sides of the conductors disposed so as to form a tubular chamber with the conductors. A movable, electrically conductive member is disposed within the tubular chamber and is adapted to engage each of the pair of conductors. By causing current to flow through the movable member, and by applying a magnetic field whose direction is transverse to the direction of current through the movable member and to the path defined by the tubular chamber, the movable member is caused to move through the tubular chamber. Electrical contacts having ends disposed in the tubular chamber can be connected periodically to at least one of the spaced-apart conductors by the movable member during the latters movement. Thus, current can be interrupted periodically in a circuit that includes one or more of these contacts and one of the spaced-apart conductors. The width, number, and spacing of the electrical contacts within the tubular chamber determine, in part, the waveform and frequency of the interrupted current. The make and break frequency of the switching device can also be varied by controlling the amplitude of current and/ or the strength of the magnetic field with respect to the movable member.

The novel features of the present invention, both as to its organization and method of operation, as well as additional objects and advantages thereof, will be more readily understood from the following description, when read in connection with the accompanying drawing, in which:

FIG. 1 is a plan view of one form of switching device according to the present invention connected in a schematically shown circuit for interrupting a direct current in a manner whereby it may be transformed by a transformer;

FIG. 2 is a cross-sectional view of the switching device, taken along the line 2-2 in FIG. 1, and connected in a schematically shown circuit for providing a magnetic field in accordance with the present invention; and

FIG. 3 is a fragmentary view of a portion of the switching device of FIG. 1, showing another embodiment thereof for varying the waveform of current interrupted by the switching device.

Referring, now, particularly to FIGS. 1 and 2 of the drawing, there is shown a switching device 10 wherein an electrically conductive, movable member 12 is adapted to move between, and in contact with, spaced-apart, electrical conductors 14 and 16. The conductors 14 and 16 are preferably flat, washer-like rings that are supported in a parallel relationship by concentric ring insulators 18 and 26. The insulators 18 and 20 are disposed on opposite sides of, that is, adjacent to the inner and outer peripheries of the conductors 14 and 16 and fixed to the latter by any suitable means, such as epoxy adhesives, to form an endless tubular chamber 22.

The movable, or rollable, member 12 is preferably a small quantity of mercury whose size is sufficient to make an electrical connection with both of the conductors 14 and 16 during its movement along the chamber 22. Means are provided to apply a source of voltage between the conductors 14 and 16 so as to cause current to flow through the movable member 12. To this end, a lead 24 is electrically connected between the conductor 16 and the positive terminal of a source 26 of voltage. The lead 24 extends through an opening 28 in a pole piece 30. The negative terminal of the battery 26 is electrically connected to the conductor 14 through a variable resistor 32 and a lead 34, the latter being connected to the conductor 14 by any suitable means, as by solder. The unidirectional current from the voltage source 26 through the movable member 12 can be controlled by varying the resistor 32.

Means are provided to produce a magnetic field whose direction is transverse to both the direction of current flow through the movable member 12 and the direction of movement of the movable member through the chamber 22. To this end, a dish-shaped, iron pot or field structure 35 is formed with a centrically located pole 38 for supporting a coil id thereon around the pole 38, as shown in FIG. 2. The pole piece 30 is disc-shaped and is fixed to the pole 33 by a screw 42. The pole piece 30 is also disposed concentrically within the ring insulator 20 and may be fixed to the latter by a suitable adhesive. An annular pole piece 44 is secured to the open end of the pot 36 by screws 46, 4'7, 48 and 49. The pole piece 44 is concentrically disposed around the ring insulator 18 so as to provide, with the pole piece 30, a magnetic field within the tubular chamber 22. In the switching device 10, the direction of the magnetic field at any point in the chamber 22 is substantially that along a radius from the center of the pole piece 36 and including such point. Thus, the direction of the magnetic field may be said to be substantially perpendicular to the path defined by the tubular chamber 22.

One end lead 50 of the coil 40 is connected directly to the positive terminal of a source 52 of unidirectional voltage, and the other end lead 54 of the coil 40 is connected to the negative terminal of the voltage source 52 through a variable resistor 56. It will now be understood that the intensity of the magnetic field can be consneer/a trolled by varying the current through the coil 46 by means of the variable resistor 56. It is also within the contemplation of the present invention to provide a magnetic field through the tubular chamber 22 by a permanent magnet. If, for example, the pole 38 in the pot 36 were a permanent magnet, a magnetic field would be produced in the chamber 22 that is transverse to the direction of current flow through the movable member 12.

The movable member 12 is caused to move through the chamber 22 when current is sent through it in one direction and when it is disposed in a magnetic field whose direction is transverse to the direction of the current through it. The direction of motion of the member 12 is then transverse to the directions of both the current and the magnetic field. By varying either the current through the movable member 12 or the intensity of the magnetic field, as by varying resistors 32 or 56, respectively, the speed of movement of the movable member 12 is controlled. The direction of movement of the movable member 12 may be reversed by reversing either the direction of the current or the direction of the magnetic field through it. The direction in which the movable member 12 tends to move may be determined by Flemings left hand rule. For example, the forefinger, second finger, and thumb, placed at right angles to each other, represent, respectively, the directions of magnetic flux, electromotive force, the motion with respect to the movable member 12.

Means are provided to make an electrical contact between at least one of the conductors 14 and 16 and one or more electrical contacts that extend to the chamber 22. While only four electrical contacts 60, 61, 62 and 63 are shown in FIG. 1, it is to be understood that this number is merely illustrative, and that the actual number in any embodiment will be determined by the particular application of the device 16. The electrical contacts 66-63 eX- tend through holes in the conductor 14 and are insulated from the conductor 14 by any suitable insulating material, such as an insulating epoxy adhesive. It will now be observed that, as the movable member 12 moves through the chamber 22, an electrical connection is made sequentially between the conductor 16 and the contacts 69, 61, 62 and 63 during one revolution of the movable member 12. The possible number of electrical contacts is limited only by the physical size of the device 10. The contacts 60 and 61, for example, may be placed very close to each other so that an electrical connection may be made between them by the movable member 12 as the latter moves between them, if so desired. Also, it is within the contemplation of the present invention for an electrical connection to be made sequentially between each of the contacts 60-63 and the electrical conductor 14 as the movable member 12 moves through the chamber 22.

Referring, now, particularly to FIG. 1, there is shown a circuit for interrupting current from a unidirectional voltage source 64 in a manner whereby it may be transformed by a transformer 66 as, for example, in a D.-C. to A.-C. converter. The positive terminal ofthe voltage source 64 is connected to the conductor 16 through the lead 24-, and the negative terminal of the voltage source 64 is connected to each of the contacts 60, 61, 62 and 63 through a variable resistor 68 and the primary winding 76 of the transformer 66.

In operation, the movable member 12 is caused to move continuously through the chamber 22 by sending current through it from the voltage source 26 and by producinga magnetic field by means of current from the voltage source 52. As the movable member 12 passes each of the contacts 66, 61, 62, and 63, it connects them with the conductor 16, thereby sending pulses of current from the voltage source 64 through the primary winding 70. The alternating voltage produced by the interrupted current through the primary winding 76 is transformed by the transformer 66 to provide an alternating, transformed voltage across the secondary winding 71 of the transformer 66. By controlling either the current through themovablc member 12, the strength of the magnetic field, or the number and spacing of the electrical contacts, the frequency and the waveforms of the interrupted current pulses can be controlled.

The waveforms of the pulses of interrupted current from the voltage source 6 1 may also be controlled by employing electrical contacts of different shapes. Referring, now, to FIG. 3, there is shown an elongated contact 72 disposed in the conductor 14 and insulated therefrom. A contact '74, of relatively smaller cross-sectional area than the contact 72, is also disposed in the conductor 14 and insulated therefrom. The contacts 72 and 74 extend to the chamber 22. It will now be observed that, with the arrangement shown in FIG. 3, the duration of the electrical connection that may be made by the movable member 12 between the conductor 16 and the contact 72 will be relatively much longer than that between the conductor 16 and the contact 74, assuming that the rate of travel of the movable member 12 is substantially constant. Thus, when the movable member 12 travels in one direction, as, for example, in the direction'indicated by the arrow 76, the switching device 16 can close aicircuit (not shown) in a manner to generate pulses corresponding to the letter N in the Morse code. When traveling in the direction indicated by the arrow 78, the movable member 12 can close a circuit (not shown) in a manner to generate pulses corresponding to the letter A in the Morse code.

From the foregoing description, it will be apparent that there has been provided an improved switching device for making and breaking an electrical circuit periodically with a frequency that is controllable. While only a limited number of embodiments and applications of the switching device of the present invention have been described, variations coming Within the spirit of this invention will, no doubt, readily suggest themselves to those skilled in the art. For example, the movable member may be made to roll along a channeled path, not necessarily tubular, that includes the pair of conductors for applying current to the movable member. Hence, it is desired that the fore going description of the invention shall be considered as illustrative and not in a limiting sense.

What is claimed is:

1. A switching device comprising (a) a pair of parallel, looped conductors having inner and outer peripheries,

(b) insulating means extending between said peripheries of said conductors and forming an endless, tubular chamber therewith,

(c) a movable quantity of mercury disposed in said chamber and adapted to engage said pair of conductors,

(d) means to apply a voltage between said conductors to cause current to flow through said mercury,

(e) means to apply a magnetic field in said chamber, said magnetic field having a direction transverse to the direction of said current, and

(f) at least one electrical contact extending to said chamber and adapted to be engaged by said mercury during its movement, whereby an electrical connection can be made between at least one of said conductors and said contact.

2. Aswitching device comprising (a) a pair of parallel, looped conductors having inner and outer peripheries,

(b) means insulated from said conductors extending between said peripheries of said conductors and forming an endless, tubular chamber therewith,

(c) a movable electrically conductive member disposed in said chamber and adapted to engage said pair of conductors,

(d) adjustable means to apply a voltage between said conductors to cause current to fiow through said member,

(-e) adjustable means to apply a magnetic field in said chamber, said magnetic field having a direction trans-verse to the direction of said current and to the direction of movement of said member, and

(f) a plurality of electrical contacts extending to said chamber and adapted to be engaged by said member during its movement, whereby an electrical connection can be made between at least one of said conductor-s and said contacts.

3. Apparatus for making and breaking a circuit, said apparatus comprising (a) a pair of spaced-apart, annular electrical conductors,

(b) insulating means extending between portions of said conductors and forming an annular, tubular chamber therewith,

(c) a roll=able, electrically conductive member disposed within said chamber and adapted to engage said conductors during its rolling movement,

(d) means to produce a magnetic field in said chamber,

(e) means to cause current to flow through said member in a direction transverse to the direction of said magnetic field to cause said member to move in said chamber,

(f) an electrical contact extending to said chamber and adapted to engage said member during its move ment, and

(-g) means to connect said circuit in series with said contact and one of said conductors.

4. Apparatus for making and breaking a circuit, said apparatus comprising (a) a pair of spaced-apart, annular electrical conductors,

(b) means extending between portions of said conductors and insulated therefrom, said means forming an endless tubular chamber with said conductors,

(c) a rollable, electrically conductive member disposed Within said chamber and adapted to engage said conductors during its movement,

(d) means to produce a magnetic field in said chamber, said last-mentioned means comprising means to vary the intensity of said magnetic field,

(e) variable means to cause current to flow through said member in a direction transverse to the direc tion of said magnetic field, whereby to cause said member to move in said chamber,

(1) a plurality of contacts extending to said chamber and adapted to be engaged by said member during its movement, and

(g) means to connect said circuit sequentially in series with each of said contacts and one of said conductors.

5. An electrical control device comprising (a) an endless, hollow member comprising a plurality of endless electrical conductors and means for insulating said conductors -from each other,

E (b) a mass of electrically conductive material Within said member occupying a small portion of the volume thereof, said mass making electrical contact with said conductors and being movable along said member,

(0) means for applying a voltage between said conductors for causing a current to flow through said mass,

(d) means for applying a magnetic field to said member transverse to the direction of said current flow and the direction of movement of said mass,

(e) at least one contact so disposed as to be engaged by said mass as said mass moves along said member, and

(f) means for insulating said contact from said conductors,

(g) said mass providing an electrical connection between said contact and at least one of said conductors upon engagement of said contact by said mass as said mass moves along said hollow member.

Cir

6. An electrical switching device comprising (a) an annular, hollow member comprising a plurality of annular electrical conductors and means for insulating said conductors from each other,

(b) a mass of electrically conductive material within said member occupying a small portion of the volume thereof, said mass making electrical contact with said conductors and being movable along said member,

(c) means for applying a voltage between said conductors for causing a current to flow through said mass,

(d) means for applying a magnetic field to said member transverse to the direction of said current flow and to the direction of movement of said mass,

(e) at least one contact so disposed as to be engaged by said mass as it moves along said member,

(f) means for insulating said contact from said conductors, and

(g) means by which an electrical connection is completed between said contact and at least one of said conductors upon engagement of said contact by said mass as said mass moves along said annular member.

7. An electrical switching device comprising (a) an annular, hollow member comprising a plurality of endless electrical conductors and means for insulating said conductors from each other,

(-b) a quantity of mercury within said member occupyting a small portion of the volume thereof, said mercury making electrical contact with said c'onductors and being movable along said member,

(c) means for applying a voltage between said conductors for causing a current to flow through said mercury,

(d) means for applying a magnetic field to said memtber transverse to the direction of said current flow and to the direction of movement of said mercury,

(e) at least one contact so dispersed as to be engaged by said mercury as it moves along said member,

( f) means insulating said contact from said conductors,

(g) said mercury completing an electrical connection between said contact and at least one of said conductors upon an engagement of said contact by said mercury as said mercury moves along said annular member, and

(h) means for applying voltage between said one conductor and said contact 8. An electrical switching device comprising (a) an annular, hollow member comprising a pair of endless electrical conductors and means for insulatting said conductors from each other,

(b) a mass of electrically conductive material within said member occupying a small portion of the volume thereof, said mass malsing electrical contact with said conductors and being movable along said member,

(0) means for applying a voltage between said conductors for causing a current to flow through said mass,

(d) means for applying a magnetic field to said member transverse to the direction of said current flow and to the direction of the movement of said mass,

(e) at least one contact so disposed as to be engaged by said material as it moves along said member,

( f) means for insulating said contact from said two conductors, an electrical connection being completed between said contact and at least one of said conductors only upon an engagement of said contact by said material as said material moves along said annular member, and

(g) means for applying a voltage between said one conductor and said contact.

9. An electrical control device comprising (a) a pair of endless, spaced-apart electrical conductors,

(b) electrically conductive means in bridging engagement with said conductors and movable therealong in a fiXed path,

(0) means for applying a voltage between said conductors for causing a current to flow through said conductive means,

(d) means for applying a magnetic field to said member transverse to the direction of said current flow and to the direction of movement of said conductive means,

(e) at least one contact disposed along said path for engagement by said conductive means during its movement, and

(f) means for insulating said contact from said conductors to cause an electrical connection to be made between said Contact and at least one of said conductors only upon an engagement of said contact by said means as said means moves along said path.

510. An electnical control device comprising (a) and endless, hollow member comprising a pair of spaced-apart, endless, electrical conductors and means lfior insulating said conductors from each other,

(b) a mass of electrically conductive material within said member occupying a small portion of the volume thereof, said mass making electrical contact with said conductor and being movable along said member,

( o) means for applying a voltage between said conductors for causing a current to flow through said mass,

(d) a magnetic field structure for applying a magnetic field to said member transverse to the direction of said current flow and to the direction of the movement of said mass,

(e) at least one contact so disposed as to be engaged by said mass as it moves along said member, and f) means for insulating said contact from said conductors so that an electrical connection is completed between said contact and at least one of'said coniductors only upon engagement of said contact by said mass as said mass moves along said path.

11. An electrical control device comprising (a) an endless, hollow member comprising a pair of spaced-apant, endless, electrical conductors and means t'or insulating said conductors from each other,

(b) a mass of electrically conductive material within said member occupying a small portion of the volume thereof, said mass making electrical contact with said conductors and being movable along said member,

(c) means for applying a voltage between said conductors for causing a current to flow through said mass,

((1) a magnetic field structure for applying a magnetic .field to said member transverse to the direction of said current flow and to the direction of movement of said mass, said field structure comprising:

(1) a pot of magnetic material having a central pole and an outer pole therearound and spaced from said central pole to provide ,a space between said poles in which said endless member is disposed,

(2) a coil between said poles and around said central pole, V 7.

(3) means for applying a voltage across said coil for inducing a magnetic field in said field structure and thereby applying said magnetic field to said endless member,

(e) at least one contact so disposed as to be engaged by said mass as it moves along said member, and (-f) means for insulating said contact from said c'onductors in a manner to complete an electrical conmotion between said cont-act and at least one of said conductors upon engagement of said contact by said mass as said mass moves along said path.

7 References Cited by tlle Examiner UNITED STATES PATENTS 1,773,036 8/30 Fitzgerald 200-112 X 2,158,009 5/ 39 Hufn-agel 2001l2 X 2,859,303 11/58 Anderson 200-ll2 3,029,323 4/62 Carlson 2001l2 BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCHAEFER, Examiner. 

1. A SWITCHING DEVICE COMPRISING (A) A PAIR OF PARALLEL, LOOPED CONDUCTORS HAVING INNER AND OUTER PERIPHERIES, (B) INSULATING MEANS EXTENDING BETWEEN SAID PERIPHERIES OF SAID CONDUCTORS AND FORMING AN ENDLESS, TUBULAR CHAMBER THEREWITH, (C) A MOVABLE QUANTITY OF MERCURY DISPOSED IN SAID CHAMBER AND ADAPTED TO ENGAGE SAID PAIR OF CONDUCTORS, (D) MEANS TO APPLY A VOLTAGE BETWEEN SAID CONDUCTORS TO CAUSE CURRENT FLOW THROUGH SAID MERCURY, (E) MEANS TO APPLY A MAGNETIC FIELD IN SAID CHAMBER, SAID MAGNETIC FIELD HAVING A DIRECTION TRANSVERSE TO THE DIRECTION OF SAID CURRENT, AND (F) AT LEAST ONE ELECTRICAL CONTACT EXTENDING TO SAID CHAMBER AND ADAPTED TO BE ENGAGED BY SAID MERCURY DURING ITS MOVEMENT, WHEREBY AN ELECTRICAL CONNECTION CAN BE MADE BETWEEN AT LEAST ONE OF SAID CONDUCTORS AND SAID CONTACT. 